The invention relates to a method for determining a bite point of a hybrid clutch of a hybrid vehicle, which is actuated by a hydrostatic clutch actuator, with the hybrid clutch disconnecting or connecting an internal combustion engine and an electric motor, and the bite point being detected by a slow actuation of the hybrid clutch, starting from a separating position of the hybrid clutch which it assumes in an idle state, upon a defined torque reaction of the electric motor.
DE 10 2010 024 941 A1 discloses a method for controlling a duplex clutch—transmission with at least two partial drive trains, allowing each of them to be coupled via a clutch to an internal combustion engine. During drive operation of the vehicle comprising the duplex clutch—transmission, a bite point of the clutch is determined independent from the motor torque. This bite point is here determined during the start of operation of the vehicle and then adapted during operation of the vehicle.
In a hybrid vehicle with a hybrid drive train the driving resistance can be overcome by mechanical energy from two independent energy sources, such as fuel of an internal combustion engine and electric energy from a traction battery of an electric motor. According to DE 10 2008 030 473 A1 a method is known for determining the bite point of an automatic hybrid clutch in a hybrid drive train. The bite point of the hybrid clutch, which is arranged between an internal combustion engine and an electric traction drive, is determined when the internal combustion engine is stationary by slowly closing the hybrid clutch and evaluating the influence of the closing hybrid clutch upon the electric machine of the electric traction drive, which rotates with a predetermined speed.
The quality of the bite point detection largely depends on the quality of the regulator of the electric motor used, because attention is given only and exclusively to the reaction of the speed controller of the electric motor used. This means that all weaknesses of the controller, such as reaction time, superimposing vibrations, oscillation behavior, must be corrected by adjusting the adaption routine. For this reason waiting times are provided until the controller of the electric motor has reached its stationary condition. Furthermore, speed controllers frequently incite oscillations of different frequencies. In order to eliminate them, the torque signal must be filtered, which additionally slows down the determination of the bite point, because tuning the filter also requires some time.